The Turing test is a test devised by Alan Turing in 1950 for determining whether a machine can think. The Turing test tested whether a machine could exhibit intelligence that is equivalent to, or indistinguishable from the intelligence of a human. The Completely Automated Public Turing Test to Tell Computers and Humans Apart (CAPTCHA) test is often regarded as a type of reverse Turing test, which is a test administered by a computer to detect whether the party providing the answer to a question is a human or a machine. Since a computer is often unable to answer a CAPTCHA question, a party that provides the correct answer to the question can be regarded as a human. For example, the computer presents a twisted image that includes a verification code, which a human or a machine attempts to recognize. A party who can recognize the verification code correctly is determined to be a human. A party who cannot recognize the verification code is determined to be a machine.